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Патент USA US3088901

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May 7, 1963
F. e. FOOTE ETAL
3,088,891
FUEL ELEMENTS FOR NEUTRONIC REACTORS
Filed March 4, 1949
3 Sheets-Sheet 1
May 7, 1963
F. G. FOOTE Em
3,088,891
FUEL ELEMENTS FOR NEUTRONIC REACTORS
Filed March 4. 1949
'
5 Sheets-Sheet 2
INVENTOR5-'
BY f'r'azz/Z’ ¢Foote
May 7, 1963
F. G. FOOTE ETAL
3,088,891
FUEL ELEMENTS FOR NEUTRONIC REACTORS
Filed. March 4, 1949
3 Sheets-Sheet 3
4
1:13;?
Z0
Z4
3,988,891
Patented May 7, 1963
2
3,088,891
FUEL ELEMENTS FOR NEUTRONIC REACTORS
Frank G. Foote, Chicago, 111., and Eric R. Jette, Los
Alamos, N. Mere, assignors to the United States of
America as represented by the United States Atomic
of development of defects in the bonding so provided,
“hot spots” will develop at the surface of the ?ssionable
material at points where the heat transfer is inadequate,
and the ?ssionable material may melt or suffer undesir
able chemical reactions with the bonding material or the
jacket. The provision of a suitable bond for maintaining
heat transfer between the ?ssionable material and the
jacket, and thus between the ?ssionable material and, the
coolant, has been one of the major problems in the de
This invention relates to neutronic reactors. More 10 sign and construction of neutronic reactors.
Accordingly, it is the principal object of the present
speci?cally the invention relates to an improved fuel ele
Energy Commission
Filed Mar. 4, 1949, Ser. No. ‘79,703
2 Claims. (Cl. 204-154.2)
invention to provide an improved form of bond or heat
transfer medium between a body of ?ssionable material
and a jacket or can enclosing such material, for use in
chain reaction occurs by ?ssion of a thermally ?ssionable
material (i.e. a material containing an isotope ?ssionable 15 a neutronic reactor. The invention will best be under
stood by description of a single embodiment thereof as
by thermal neutrons). In the so-called “thermal” reactor,
ment structure for neutronic reactors.
As is by now well known, in a neutronic reactor, a
the chain reaction is sustained by ?ssion of the thermally
?ssionable isotopic content of the thermally ?ssionable
material by thermal neutrons, i.e. neutrons having no
energy other than that which they possess by reason of
temperature. In such reactors, there is incorporated a
moderator material in which the ?ssionable material is
dispersed, either homogeneously or as aggregated bodies.
In the “fast” reactor, little or no moderator is incorpo
illustrated by the attached drawing, in which:
FIG. 1 is a plan view, partially broken away, of a
reactor fuel element embodying the invention;
FIG. 2 is a side elevation, partially broken away, of
the fuel element of FIG. 1;
FIG. 3 is a cross-sectional view of the fuel element
of FIG. 1 illustrating the placing of the fuel element in
a coolant channel of a neutronic reactor;
FIG. 4 is a fragmentary cross~sectional view of a neu
rated, and the chain reaction is maintained by ?ssion 25
tronic reactor incorporating the fuel element of FIG. 1;
caused by “fast” neutrons, i.e. neutrons of high energy.
Reactors may also be so designed that the bulk of the
nuclear ?ssions are produced by neutrons of intermediate
FIG. 5 is a plan section of the reactor of FIG. 4 taken
along the line 5-5 in the direction indicated by arrows;
and
energies.
P16. 6 is a vertical sectional view taken along the line
It will be understood that the present invention is not 30
6—6 of FIG. 4.
concerned with the nuclear phenomena by which a chain
The jacketed fuel element 8 of FIGS. 1, 2, and 3 is a
reaction is obtained, nor with such design features as
?at rectangular slab 11) of natural or isotopically en
critical dimensions, purity, choice of moderator or ?ssion
riched uranium or plutonium encased in a jacket 12 of
able material, or the pattern or “geometry” in which the
?ssionable material is disposed in order to produce the 35 aluminum or stainless steel. The jacket 12 is formed
chain reaction.
Such criteria for the operativeness of a
of an upper recessed member 14 and a lower recessed
member 16, both of which have ?anges 18, the ?anges 18
being super-imposed and being welded all around the
in the neutronic reactor art, and are disclosed in the co
perimeter to form a pressure-tight jacket for the uranium
pending application of Enrico Fermi and Leo Szilard,
Serial No. 568,904, ?led December 19, 1944, now Patent 40 body 10. The jacket 12 is provided with longitudinal
ribs 21) on the upper and lower surfaces. All voids within
No. 2,708,656, issued on May 17, 1955.
the jacket 12 left unoccupied by the ?ssionable material
Neutronic reactors are commonly cooled by heat ex
neutronic reactor are now well known to persons skilled
change between the ?ssionable material and a ?uid cool
10 are ?lled with a thermally conductive liquid 26. The
?lling and sealing may be accomplished by ?rst welding
cooled. In order that the ?ssionable material not ‘be 45 three edges of the jacket 12, then inserting a ?ne needle
through the unwelded edge with the unwelded edge placed
chemically affected by the coolant, and in order that the
uppermost, ?lling the jacket 12 under pressure slightly
coolant not become contaminated with ?ssionable ma
greater than atmospheric pressure, and ?nally completing
terial or with highly radioactive ?ssion products, the ?s
the closure by welding. Preferably precautions are taken
sionable material which is usually called a slug is usually
ant, which is ?owed through the reactor and externally
insulated from ?owing coolant by a barrier such as a
jacket or can. The jacket or can must be of a thermally
conductive material in order to preserve a high rate of
heat exchange between the ?ssionable material and the
to avoid the entrapment of air within the jacket 12.
Preferably the liquid which establishes thermal contact
between the uranium body It) and the jacket 12 is a
thermally conducting metal having a melting point lower
than 100° C. It is also desirable that the bonding mate
must have a relatively low cross-section for capture of 55 rial have low neutron adsorption characteristics. Exem
plary of such metals are sodium and sodium-potassium
neutrons, in order that the chain reaction not be pre
alloys.
vented by high neutron absorption in non-?ssionable ma
FIGS. 4, 5 and 6 illustrate schematically a neutronic
terials. Aluminum and stainless steel are commonly em
reactor incorporating the fuel element described above.
ployed as such jacketing materials. Neither the choice
The active portion of the reactor is enclosed within a
of jacketing material, nor the maximum thickness or
cylindrical pressure shell 30 having end walls 32. The
minimum purity thereof required in order that the chain
pressure shell 30 is surrounded by a neutron re?ector 34,
reaction may be maintained constitutes any portion of
for example of graphite. Within the shell 31) is a mass
the present invention, being determinable in accordance
24- of a moderator material such as beryllium. Coolant
with criteria set forth in the copending application re
ferred to above, and now well known in the neutronic re 55 ?ow and fuel passages 22, rectangular in cross section,
extend through the moderator mass 24. The jacketed
actor art.
fuel members 8 are placed within the passages 22, as
Where the ?ssionable material is incorporated in the
shown in detail in FIG. 3. The end walls 32 of the pres
jacket and operation at any considerable level of power
sure shell 30 are apertured to receive rectangular pipes
(heat generation in the ?ssionable material) is required,
it is necessary that the ?ssionable material be “bonded” 70 36 which form inlet and outlet passages to the respective
coolant and fuel channels 22. The coolant pipes 36 are
to the jacket in order that uniform heat transfer be main
joined to the end Walls 32 of the shell 30 in pressure
tained. In the absence of such bonding, or in the event
coolant.
In addition the material of the jacket or can
3,088,891
4
3
tight fashion, as by welding. At the outlet end of each
channel 22 is positioned a vertical pin 38 which retains
the jacketed fuel member 8 within the shell 30 against
the pressure of the coolant. *It will be understood that
the coolant is not illustrated in the drawing, the choice
of coolant, like the choice of ?ssionable material, jacketing material, dimensions, and critical size being by now
well within the skill of the art.
As is likewise indicated schematically in the drawing,
such fuel elements, which may readily be designed. A
single embodiment has herein been illustrated and
described in accordance with the patent statutes. How
ever the extent of patent protection to be accorded the
invention should be determined not by the particular
embodiment herein disclosed, but by the claims hereto
appended.
~What is claimed is:
1. As an article of manufacture, a slug jacket con
there is provided a control rod 40 of a neutron absorbing 10 taining a unitary core of ?ssionable material and a
material, such as boron, cadmium, or compounds thereof,
which protrudes into the shell 30 and which may be
inserted or withdrawn to reduce or increase the reactivity
of the reactor. ‘The control rod 40 operates in a well
42 which enters the shell 30 through a pressure-tight
welded seal at 44. The control rod 40 may be cooled
by the ?owing of helium in the well 42.
By incorporation of the liquid metal bond 26 there are
eliminated the problems which arise with the bonding
agents heretofore employed. The lique?able metal bond 20
is self-healing and effectively acts to prevent the develop
ment of faulty portions of the thermal bonding between
the body of ?ssionable material 10 and the jacket 12.
Although, as stated above, the metal of the bond 26
preferably has a melting point below 100° C., it will 25
be understood that it is within the purview of the inven
tion to employ a metal of higher melting point and to
lique?able metal bond of a metal of the group consisting
of sodium and sodium-potassium alloys.
2. As an article of manufacture, a slug jacket con
taining a unitary core of thermally ?ssionable material
surrounded by a lique?able metal bond of a sodium
potassium alloy.
References Cited in the ?le of this patent
UNITED STATES PATENTS
1,202,162
Clay _______________ __ Oct. 24, 1916
233,011
861,390
Switzerland ___________ __ Oct. 2, 1944
France ______________ __ Feb. 7, 1941
FOREIGN PATENTS
OTHER REFERENCES
Smyth: A General Account of the Development of
operate the neutronic reactor at a temperature above
Method of Using Atomic Energy for Military Purposes
the melting point of the material of the bond 21’: but
below the melting point of the ?ssionable body 10 or
the jacket 12.
Persons skilled in the art will readily understand that
the embodiment of the invention herein illustrated is only
Under the Auspiccs of the United States Government,
1940-1945, pp. 84 and 106. Publ. Aug. 11-12, 1945,
U.S. Government Printing Office.
Kelly et al.: Phy. Rev. 73, 11-35-9 (1948).
one of a vast number of ‘fuel elements employing the
Liquid-Metals Handbook, Navexos, p. 733, June 1,
1950, Atomic Energy Commission-Department of the
liquid bond of the invention, and of reactors employing 35 Navy, ?rst edition, pp. 46, 47.
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